My '15 has nav with H/K speakers and an amp, and I'm quite happy with the way it sounds. I've never heard the base unit of either model year so I can't compare the H/K system to that. I assume the '15 H/K system is the same unit that's in the '16 models. As far as I know, only the base non-nav head unit got upgraded for the new model year.
I'm gonna have to check, but I think I recall it having an equalizer, albeit somewhat simplistic. It's been over a year since I set things, but I'm virtually certain it has more than just bass, mid, and treble. Seems like there were 7 or 8 difference frequency bands that could be set.
But I'm pretty pleased with the sound. When you go aftermarket, there could very well be problems with steering wheel controls, so the cost of harnesses and such to maintain full steering wheel control capability can be considerably more than just the cost of the head unit.